Preparing metallic components for solder joining requires significant preparation of the surfaces such that the solder wets these components cleanly and ensures a high strength bond. These components may be treated with an agent such as a flux that will clean the component, remove any tarnish, protect the component from further tarnishing, and promote the wetting of the solder onto the component. Additionally, a component may be pre-coated with the correct amount of solder required to complete the soldering process, thus potentially facilitating the joining process.
The most common coatings used to ensure solderability include a solder, silver, gold or a combination of metals such as nickel and gold. The choice of coatings and coating process depends on the environmental conditions the component must survive, the complexity of the component, and budget. For many components a coating of solder is effective and can be applied from molten solder via a variety of processes such as dipping the component in a bath of solder, solder fountain, solder wave, or by being sprayed by molten solder. If the amount of solder must be controlled, processes such as hot air solder leveling, roller tinning and solder dispensing can be used to transfer molten solder. If even more control is required and a higher cost process is acceptable, solder can be applied by electroplating which can achieve a uniform coating with finely controlled thickness. Yet, there remains a need for further control of solder application, for various types components where cost is critical and/or where features present difficulties in attaining the desired solder specifications.